Traditional multi-stage high rate fracture treatments have been used in many shale and conventional formations. These treatments typically rely on composite bridge or frac plugs, run on wireline to provide zonal isolation. In a typical frac treatment, rates of up to 100 bpm are normally divided between four to six pre-perforated clusters per stage. Typical spacings between clusters are 50 to 100 ft. In theory, fluid would divide equally between each perforated cluster, however that is an unlikely scenario since stimulation treatments will follow the path of least resistance. To improve production results, targeted fracturing operations are gaining in popularity in many formations.
Some targeted operations utilize abrasive perforating via coiled tubing (CT), followed by the fracture treatment down the annulus. The treatment flush is modified to include an underdisplaced dense slurry stage to act as the isolation mechanism. In vertical wells, proppant settles by gravity covering the recently treated interval. In horizontal wells however, a plug enhancement additive (PEA) can be used to achieve isolation, partially mitigating gravity effects. Moreover, instead of splitting flow between four to six clusters, most horizontal treatments target only one discreet cluster/zone at a time. Significant gains in fracture control are obtained with this method. Initial targeted operations were applied to 300 ft of frac spacing, thus reducing the number of stages per well when compared to the 50 to 100 ft cluster spacing on higher rate frac operations.
This paper describes one targeted operation in a horizontal well where the spacing was reduced to 60 ft. In all, forty-three stages were successfully stimulated using enhanced sand plugs for zonal isolation.